How long is the maximum period between ablution and the two rak'ahs of ablution, and is it permissible to perform them after being busy for an hour?

The Sunnah of ablution (wudu’) is missed by turning away from it, or by becoming preoccupied with something else, or by a ritual impurity (hadath), or by a lengthy customary separation between it and the wudu’, as no specific time limit has been set for this separation. If it is missed, it is not to be made up.